The present invention relates to a thermal transfer recording apparatus wherein an inked ribbon and a recording paper are overlapped and urged against a platen roller with the inked ribbon outside, and recording paper is recorded or printed by applying heat onto the inked ribbon by means of a thermal head while the platen roller is rotated by a driving motor through the medium of a power transmitting device. More particularly, in the present invention relates to a thermal transfer recording apparatus having an improved reduction ratio changing over mechanism useful for the power transmitting device for the platen roller.
In a conventional reduction mechanism of a power transmitting device for transmitting rotational power from a driving motor to a platen roller used for a thermal transfer apparatus, since the reduction mechanism was connected to the driving motor with a constant reduction ratio, in order to shorten or reduce non-printing time such as required for introduction and ejection of the recording paper, a method in which the rotational speed of the driving motor is increased to rotate the platen roller faster has been used. However, in this method, since the reduction ratio of the reduction mechanism is constant or unchangeable and the output of the driving motor is limited, the total recording time could not be reduced beyond a certain degree. Thus, in order to still further reduce the total recording time to obtain a high speed recording apparatus, it was required to utilize a driving motor having a higher output and capable of rotating at higher speed, which was large-sized and expensive. Further, in the conventional thermal transfer recording apparatus, since the rotation of the platen roller was regulated by the reduction mechanism, when the recording paper was jammed in a path of movement thereof and/or the inked ribbon was caught by the platen roller, the jammed recording paper or inked ribbon could not be removed unless a part of the power transmitting device or a guiding means for the recording paper was dismantled; thus, in this case, a great deal of time and labor were required to restore the recording apparatus to the original or normal state. In order to relieve the above inconvenience, a technique in which the guiding means for the recording paper is constituted by a plurality of parts and is openable for access to the periphery of the platen roller has been proposed. However, this technique has a disadvantage that the recording paper guiding means is complicated and a large space is required to permit the swinging movement of the guiding means, thereby preventing or opposing to the compactness and cost reducing of the apparatus. These conventional techniques are described in, for example, the Japanese Patent Publication Nos. 60954/1982 and 52756/1981.
Accordingly, an object of the present invention is to provide a thermal transfer recording apparatus having a power transmitting device which can eliminate the above-mentioned conventional drawbacks and which is inexpensive, and which can reduce the total recording time and easily cope with the jamming of the recording paper and inked ribbon.
The above object of the invention is achieved by providing a power transmitting device for transmitting the power from the driving motor to the platen roller in which the rotational speed of the platen roller can be changed by a reduction ratio changing-over mechanism and which has a neutral position where the platen roller can be rotated freely.
Therefore, according to the present invention, the platen roller can be rotated at high speed even during the non-printing period such as required for introduction and ejection of the recording paper, thereby reducing the total recording time of the thermal transfer recording apparatus. Further, since the platen roller can be freely rotated by bringing the power transmitting device to the neutral position, the jamming of the recording paper and/or inked ribbon can be easily removed, thereby swiftly restoring the recording apparatus to the normal conditions.
According to a preferred embodiment of the present invention, there is provided a thermal transfer recording apparatus wherein an inked ribbon and a recording paper are overlapped and urged against a platen roller with the inked ribbon outside and the recording paper is recorded by applying heat onto the inked ribbon by means of a thermal head while the platen roller is rotated by a driving motor through the medium of a power transmitting device and characterized in that said power transmitting device comprises a low speed rotational drive transmitting means for rotating the platen at low speed to perform the recording on the recording paper, a high speed rotational drive transmitting means for rotating the platen roller at higher speed than said low speed, and a rotational speed changing-over means for changing one of said low or high speed rotational drive transmitting means over to the other to connect the changed-over rotational drive transmitting means to the platen roller so that the platen roller is rotated at said low speed or at said higher speed.
Preferably, the thermal transfer recording apparatus of the present invention further includes a detecting means for detecting abnormality of the inked ribbon and/or recording paper such as a jam in a recording paper and inked ribbon moving system and a controlling means for permitting the free rotation of the platen roller by causing the rotational speed changing-over means to automatically change the power transmitting device over to its neutral position when the detecting means detects the abnormality.